Builders are desirable ingredients in powdered detergent formulations. Builders optimize the effectiveness of surfactants by several routes, one of which is by sequestering calcium, magnesium and other `hardness` ions present in the wash water that adversely affect detergency.
The manner in which detergent builders improve the cleaning powers of detergent compositions is related to a combination of factors such as emulsification of soil particles, solubilization of water insoluble materials, promotion of soil suspension in the wash water so as to retard soil redeposition, sequestration of metallic ions, and the like.
Phosphates such as tripolyphosphates and pyrophosphates have been widely used as builders due to their excellent ability to sequester `hardness` ions. However, the effect of phosphates upon the eutrophication of lakes and streams has been questioned and their use in detergent compositions has been subject to government scrutiny and regulation. Alternatives for phosphates are also widely used by detergent formulators as builders in detergent formulations. Compositions and materials change frequently as formulators attempt to improve cleaning performance while offering greater convenience in handling at lower material cost. The industry has made substantial efforts to find suitable substitutes for phosphates, however, all have one or more drawbacks that offset their value in the formulations.
In addition to builders, detergent formulations have also employed bleaches to improve soil and stain removal on clothes.
It is well known that active oxygen-releasing compounds are effective bleaching agents. These compounds are frequently incorporated into detergent compositions for stain and soil removal. Unlike the traditional sodium hypochlorite bleaches, oxygen-releasing compounds are less aggressive and thus more compatible with detergent compositions. They have, however, an important limitation; the activity of these compounds is extremely temperature dependent. Thus, oxygen-releasing bleaches are essentially only practical when the bleaching solution is heated above 60.degree. C. At a temperature of just 60.degree. C., extremely high amounts of the active oxygen-releasing compounds must be added to the system to achieve any bleach effect. Although this would indicate the desirability of high temperature operation, high temperatures are both economically and practically disadvantageous.
At bleach solution temperatures below 60.degree. C., the active oxygen-releasing compounds are rendered much less effective regardless of their level in the system. With respect to bleaching of laundry in automatic household washing machines, it must be noted that these machines are normally operated at wash-water temperatures below 60.degree. C. Consequently, a need has developed for substances which promote release of active oxygen at temperatures below 60.degree. C. These substances are generally referred to in the art as bleach precursors, although they have also been called promoters and activators. Normally, bleach precursors are used in conjunction with persalts capable of releasing hydrogen peroxide in aqueous solution, perborate being the most widely used persalt.
Typically, the precursor is a reactive compound such as a carboxylic acid ester that in alkaline detergent solution containing a source of hydrogen peroxide, e.g. a persalt, will generate the corresponding peroxy acid. The reaction involves nucleophilic substitution onto the precursor by hydroperoxy anions (HOO.sup.-) and is facilitated by precursors having good leaving groups. Often the reaction is referred to as a perhydrolysis.
There are many patents which deal with the area of bleach precursor chemistry and many of these are fully set forth in U.S. Pat. No. 4,818,426, the disclosure of which is incorporated by reference herein.
While the bleach precursors mentioned above are effective to accomplish their designed result, they still require a leaving group to activate the carbonyl carbon so as to produce the appropriate bleaching species in solution. Prior to this invention, the leaving group has not provided a significant additional washing benefit.
It has now been discovered that the leaving group can also be designed to provide a non-phosphate builder function and by judicious selection of the molecule, the leaving group can be made biodegradable and with good calcium binding ability.
1,4-Dihydro-4-oxo-2,6-pyridine dicarboxylic acid (chelidamic acid) is a well known, effective builder. In addition, we have discovered that the chelidamic acid moiety is biodegradable. The addition of chelidamic acid disodium salt to a number of acid halides which themselves contain bleach precursor molecules to generate a series of new classes of molecules is disclosed herein. These new molecules incorporate the chelidamic acid moiety as the leaving group. These new products thus provide effective metal chelation and stain bleaching simultaneously when formulated with peroxygen compounds such as sodium perborate and sodium percarbonate.
Accordingly, it is an object of the current invention to provide a multifunctional molecule which provides both good bleaching and good building.
Another object is to provide a multifunctional molecule which is both a bleach and builder precursor.
Yet another object is to provide detergent compositions employing these multifunctional molecules.